This invention is directed to missiles comprising a nose, fixed fins or movable fins, gas rudders, propelling nozzles and blast pipe inserts 5, combustion chamber liners 6, tail cone, grid fins, fluid elements and radomes or subcomponents thereof, said components being made of ceramic material.
Exposed locations such as edges, corners and tips of missiles that move at very high speeds in the near-earth atmosphere, are subject to surface temperatures of more than 1700xc2x0 C. due to aerodynamic heating. Very high temperatures in excess of 2500xc2x0 C. occur at components of missile engines the solid propellants of which sometimes burn at temperatures in excess of 3500xc2x0 C. It is desirable for the components involved to possess sufficient structural strength and functionality even at such temperatures in order to successfully complete the overall task of the missile. Until recently, the structural strength of most of the metallic components that are subject to high-temperature use was realized by employing high-temperature resistant metals and metal alloys, cooling and thermal insulation. Such measures are expensive and in all cases require additional weight so that the given task can be accomplished. In the case of mobile gear, especially missiles, any additional weight is disadvantageous so that weight-reducing solutions should be sought after.
In a known embodiment of a missile, the nose, fixed fins or movable fins, gas rudders, propelling nozzles and blast pipe inserts, combustion chamber liners, tail cone, grid fins, fluid elements and the radome are made of different metals and metal alloys. These missile components are the ones that are exposed to thermal and mechanical maximum loads.
Having regard to the current design of such missile components it is necessary due to the above-mentioned high temperatures, high mechanical loads and high pressures to use high temperature-resistant metals or metal alloys (for instance tungsten, molybdenum, Inconel) that exhibit high mechanical strength and temperature resistance. As these temperature-resistant metals and alloys will soften already at about 800xc2x0 C. with concurrent losses in strength, additional active cooling is required. Another severe drawback of the metallic components of the missile is their great weight which leads to restrictions in respect of missile acceleration and speed.
It is the object of the present invention to provide noses, fixed fins or movable fins, gas rudders, propelling nozzles and blast pipe inserts, combustion chamber liners, tail cones, grid fins, fluid elements and radomes or subcomponents thereof all made of ceramic material for use with missiles and having high resistance to temperature, pressure and abrasion, erosion resistance, low density or light weight, respectively, high thermal conductivity, low heat expansion, while permitting an almost unlimited variety of geometries and shapes.
As a solution to the specified object the nose, fixed or movable fins, gas rudder, propelling nozzles or blast pipe inserts, combustion chamber liners, tail cone, grid fins, fluid elements and the radome or subcomponents thereof of the kind specified above are characterized in accordance with this invention in that the nose 1, the fixed fins 2 or movable fins 3, the gas rudder 4, the propelling nozzles and blast pipe inserts 5, the combustion chamber liners 6, the tail cone 71 the grid fins 8, the fluid elements 9 and the radome 10, or subcomponents thereof, are made of carbon fiber-reinforced silicon carbide (C/SiC) and/or carbon fiber-reinforced carbon (C/C) and/or silicon carbide fiber-reinforced silicon carbide (SiC/SiC).
Hence the nose 1, the fixed fins 2 or movable fins 3, the gas rudder 4, the propelling nozzles or blast pipe inserts 5, the combustion chamber liners 6, the tail cone 7, the grid fins 8, the fluid elements 9 and the radome 10, or subcomponents thereof are made of fiber-reinforced ceramic material or of combinations of various fiber-reinforced ceramic materials and after infiltration will form a monolithic structure. As an overall effect, the temperature stability of these missile components is increased with a concurrent reduction in weight.
It has been found that C/SiC and/or C/C and/or SiC/SiC possess excellent strength up to high temperatures so as to permit employment even under severe conditions. In addition, besides low density there result high wear resistance, resistance to oxidation and, besides the excellent temperature stability, also high temperature cycle resistance.
The material is particularly gas and liquid-tight when the surface is provided with a protective coating.
The great variety of geometries and shapes in conjunction with low weight as well as the excellent temperature stability and the high or controlled thermal conductivity, which permit correspondingly reduced cooling capacities, should be particularly stressed. With certain missiles it is possible due to the high temperature stability of C/SiC and C/C and SiC/SiC to provide no cooling or thermal insulation at all.
There is a distinction between C/SiC and C/C and SiC/SiC with continuous fiber-reinforcement and chopped fiber-reinforced C/SiC and C/C and SiC/SiC. The former material of C/SiC or C/C or SiC/SiC, which may be laminated, compressed or wound is characterized by particularly high strength and especially low density. A surface coating may be provided in order to increase the resistance to oxidation. To this end it is preferred to apply protective coats of silicon carbide and/or silicon dioxide and/or molybdenum disilicide on the component surfaces. The latter is superfluous in the case of chopped fiber-reinforced C/SiC because this material is particularly resistant to oxidation and corrosion. Also, it exhibits extremely good thermal conductivity and features particularly high resistance to thermal shocks. It is mainly suited for mechanical treatment in its green state. In this connection, noses 1, fixed fins 2 or movable fins 3, gas rudders 4, propelling nozzles or blast pipe inserts 5, combustion chamber liners 6, cone tail 7, grid fins 8, fluid elements 9 and radomes 10 or subcomponents thereof can readily be shaped with random geometries either in a single piece or from various separate segments of C/SiC preforms and/or C/C preforms by mechanical treatment.
Advantageously, the individual segments of nose 1, fixed fins 2 or movable fins 3, gas rudders 4, propelling nozzles and blast pipe inserts 5, combustion chamber liners 6, tail cone 7, grid fins 8, fluid elements 9 and radomes 10 or subcomponents thereof are co-infiltrated or co-siliconized so as to provide the desired monolithic structure. This design is especially suited for C/SiC or C/C or SiC/SiC with chopped fiber-reinforcement, in which case the individual segments are mechanically treated prior to being co-siliconized or infiltrated, respectively. Such a missile component 1-10 can readily be joined by means of fasteners such as screws or bolts or flanges, preferably made of C/SiC and/or C/C and/or SiC/SiC. Also, cooling ducts and/or recesses having round, rectangular or slot-like cross-sections may be incorporated in the missile components 1-10 by mechanical treatment in the green state.
The method according to this invention moreover provides for hybrid-type or segment-type design of the missile components 1-10. Hybrid-type monolithic missile components are formed by mechanical treatment of blanks and sub-segments, which are preferably made of C/SiC and/or C/C and/or SiC/SiC or of appropriate combinations with continuous fiber-reinforcement and/or chopped fiber-reinforcement, and by the subsequent infiltration of these individual segments with silicon and/or silicon carbide and/or carbon.
As a further development of the invention, the inner walls of the missiles or of those missile portions that are subject to high thermal loads are lined in a suitable way with C/SiC or C/C or SiC/SiC segments and provided with cooling via cooling ducts and/or with an insulating material, preferably of C/SiC or C/C or SiC/SiC or of carbon fiber felt or graphite sheet or combinations of these, so that the temperature and pressure loads acting on the metallic missile structure will be reduced as far as possible, and said segments are co-siliconized to form a monolithic missile component 1-10. The insulating materials may also be joined to the missile components 1-10 of C/SiC and/or C/C by interposing spacers therebetween which are preferably made of C/SiC or C/C or SiC/SiC, in order to provide the desired monolithic structure.
Advantageously, the density and porosity of the C/SiC material and/or the C/C material and/or the SiC/SiC material can be controlled during infiltration or siliconizing by the amount of silicon, carbon or silicon carbide added so that C/SiC and/or C/C and/or SiC/SiC with high density and low porosity may be employed as thermomechanical support structure and/or liner material, while C/SiC and/or C/C and/or SiC/SiC with low density and high porosity may be employed as thermal insulation. In this connection it is also possible to adjust density and porosity gradients across the wall thickness of the missile components 1-10.
On account of the gas and liquid tightness of the C/SiC and/or C/C materials it is also possible to incorporate open cooling ducts in the metallic missile structure, said ducts being closed upon assembly of the C/SiC and/or C/C parts and/or SiC/SiC parts. Depending on the system used, the missile component 1-10 is manufactured of separate C/SiC and/or C/C and/or SiC/SiC segments which are subsequently co-infiltrated and/or co-siliconized with carbon and/or silicon and/or silicon carbide to form a monolithic structure, or the missile components 1-10 are made in a single piece, preferably by machining a C/SiC and/or C/C and/or SiC/SiC blank. These C/SiC and/or C/C parts and/or SiC/SiC parts may also provide the cooling ducts (if required) or the recesses for heat dissipation. The body 1-10 of C/SiC and/or C/C and/or SiC/SiC and the metallic missile structure may be joined to one another by means of appropriate connecting elements such as, for instance, bolt, screw or flange joints, preferably made of C/SiC and/or C/C and/or SiC/SiC. Possible ways in this respect are illustrated in FIGS. 2 to 9.